fanny is a euphemism for the buttocks. So the exclamation "My Aunt Fanny!" or "My great Aunt Fanny!" is to say
"My ass!" as something of a perturbed rebuttal or reply
Someone who is addicted to obtaining money and building wealth. A money addict and fanatic. Breadheads often work more than one full-time job, and some even participate in illicit activities to "obtain the bread".